Area Forecast Discussion

FXUS65 KMSO 131043
Area Forecast Discussion
National Weather Service Missoula MT
343 AM MST Wed Dec 13 2017
...Light Snow Returns to the Area Today...
...Additional Snow Accumulations Friday into Saturday...
.DISCUSSION...A quick moving weather disturbance will bring a
round of light snow to much of west-central Montana and north-
central Idaho beginning mid morning and continuing through mid
afternoon. Forecast models have trended slightly higher with snow
amounts but still amounts are expected to be light (up an inch for
most areas with isolated totals of 2-3 inches). Travelers should 
be prepared for minor travel inconveniences as roadways become 
snow covered for a time and a little extra time is needed to reach
Snow will quickly end late this afternoon with a return to valley
low clouds and areas of freezing fog later tonight continuing into
Friday morning as high pressure re-establishes itself.
A cold front is progged to drop southeastward into north-central 
Idaho and western Montana by mid to late Friday. This will
support a period of widespread snowfall, and breezy west winds 
will increase particularly for the terrain of western Montana. 
The best chance for snowfall accumulations will be over mountain 
pass locations such as Lookout, Lolo, Whitebird Hill, Lost Trail,
and Marias Passes where around 2-4 inches may be possible. Lower 
elevation valleys could see anywhere from a trace to 2 inches of 
snow Friday night through mid day Saturday. Lingering snow 
showers are expected to continue through Saturday under an active
northwest flow pattern. 
There has been a few changes to the forecast. A trend to a much 
drier pattern begins Sunday as models now indicate a quick 
rebuilding of high pressure. This may support the return of 
patchy freezing fog Sunday morning, especially for the valleys 
that have had precedent snowfall.
The next feature beginning Monday into Tuesday is forecast to 
bring snow accumulations to northwest Montana and portions of 
north-central Idaho, with breezy winds also returning over the 
western Montana terrain. Model solutions diverge dramatically 
thereafter, but an active, snowier regime over the area looks to 
be favored.
.AVIATION...Fairly widespread light snow will impact west-central
Montana and north-central Idaho mid-morning through mid-afternoon
leading to a period of reduced visibility and lower ceilings, 
impacting KMSO, KBTM, and KSMN. Abundant stratus is present across
Northwest Montana and is expected to remain an issue throughout 
much of today with an occasional light snow flurry. Precipitation
will quickly end late this afternoon with the potential for low 
stratus and areas of freezing fog to return again tonight into 
Friday morning for most valleys.